Touchpad input devices are small, touch-sensitive devices that can be used as a pointing device to replace a mouse, trackball or other cursor locator/input device in mouse-driven or other personal computers. The touchpad typically includes a small touch-sensitive screen up to 3" by 5" in size. The touchpad produces X, Y location coordinates representative of the location of the touching device (finger or inanimate object such as stylus) on its surface. The computer interprets these X,Y coordinates to locate the cursor on the computer display. The user typically controls the computer cursor location by moving the input device across the sensor surface. These touchpad devices typically include a switch or "button" underneath the pad or to the side which, when pressed, is used to emulate the selection function of the button on a mouse. In cases where the touchpad has no selection button, a tap on the sensor made immediately after completion of the cursor motion and in a location relatively close to where the cursor location movement was completed, would be interpreted as a selection action equivalent to a button click.
Most personal computer systems employing touchpads as mouse replacements also have a standard keyboard as another means of computer input. In some instances, the touchpads can be used as at least a partial replacement or supplement for the keyboard by designating areas of the touchpad to correspond to the equivalent of keystrokes or keystroke sequences. A template which fits on the surface of the touch sensitive surface of the touchpad, or beneath it if it is transparent, can be used to remind the user of the function of each area. The operator can switch the touchpad from the typical touchpad use (mouse cursor control and mouse emulation) to keyboard emulation through means of keyboard input, a menu selection on the screen, or by clicking a button on the touchpad. The user would then be able to enter a particular keystroke by touching the touchpad in the area corresponding to that keystroke and clicking the button beneath the touchpad, or tapping the sensor if there were no button. For example, if the touchpad is being used as a means of entering numbers into the computer, the template may have small areas designated with numbers and mathematical symbols. When the touchpad is in keypad mode, the system is preprogrammed to recognize a touch at the locations corresponding to those designated areas as an input of that number or operation. For example, if the operator touched the number nine on the template while clicking the touchpad switch, the computer would determine that the operator designated for entry the number nine and so would enter a nine into the system.
The advantage of using the touchpad as both a cursor-control device and a keypad is that the user can do both activities at one location and not have to move back and forth between the keyboard and touchpad. Also, if the touchpad were part of a total system design, the need to build function keys into the keyboard could be eliminated.
Although this allows the user to employ the touchpad as both a mouse emulator and a keypad, the operator must continuously manipulate the touchpad or the keyboard to command the touchpad to enter into either the mouse-emulation mode or the keypad mode; if the operator needs to switch between the use of the touchpad as a mouse emulator and a keypad, a separate step must be taken each time a change of mode is desired. As most software would require a mixed sequence of keypad entries and cursor control actions, the need to change modes makes this bi-modal use cumbersome. Accordingly, users often find it easier to simply use the standard computer keyboard for entry of letters and numbers rather than use the touchpad as both a mouse emulator and a keypad.